Fuel cell stack compression devices and methods

ABSTRACT

A spring compression assembly is configured to apply a load to a stack of electrochemical cells. The assembly includes a ceramic leaf spring, a tensioner configured to apply pressure to a first side of the spring and a bottom plate located on a second side of the spring opposite the first side of the spring. The bottom plate is configured to transfer a load from the spring to the stack of electrochemical cells.

CROSS REFERENCE TO RELATED PATENT APPLICATION

This application is a divisional of U.S. application Ser. No.12/892,582, filed Sep. 28, 2010, which claims the benefit of U.S.Provisional Application No. 61/272,494, filed Sep. 30, 2009,incorporated herein by reference in its entirety.

FIELD

The present invention is directed to fuel cell system components, suchas stack compression devices and methods.

BACKGROUND

U.S. application Ser. No. 11/656,563, filed on Jan. 23, 2007 andpublished as US published application 2007/0196704 A1 and incorporatedherein by reference in its entirety, describes a fuel cell system inwhich the solid oxide fuel cell (SOFC) stacks are located on a base, asshown in FIG. 1. Wedge shaped ceramic side baffles 220 (e.g., having anon-uniform thickness and a roughly triangular cross sectional shape inthe horizontal direction) are located between adjacent fuel cell stacks14 (or columns of fuel cell stacks). The baffles 220 serve to direct thecathode feed into the cathode flow paths and to fill the space betweenadjacent stacks so that the cathode feed passes through each of thestacks 14, rather than bypassing around the longitudinal sides of thestacks 14. The baffles 220 are held in place by tie rods 222 that passthrough closely fitting bores 224 centrally located in each of thebaffles 220. Preferably, the baffles 220 are electrically non-conductiveand made as one unitary piece from a suitable ceramic material. FIG. 1also shows fuel distribution manifolds between the stacks in the stackcolumn and fuel inlet and exhaust conduits connected to the manifolds.

In this prior art system, the SOFC stacks maintain a compressive load.The compressive load is maintained by upper pressure plate 230, tie rods222, lower pressure plate 90 and a compression spring assembly locatedbelow the lower pressure plate 90. The compression spring assemblyapplies a load directly to the lower pressure plate 90 and to the upperpressure plate 230 via the tie rods 222. The bores or feed-throughs 224through the baffles 220 act as heat sinks and thereby decrease thesystem efficiency.

In an alternative embodiment, the load is transmitted through the base239 as this is the only zero datum of the system. Penetrations orfeed-throughs through the base 239 are used in order to pull therequired load from the base 239.

SUMMARY

An embodiment relates to a baffle configured to place a load on a stackof electrochemical cells and direct a reactant feed flow stream. In oneaspect the baffle is made of a plurality of baffle plates. In oneaspect, the baffle plates have a dovetail shaped protrusion on one endand a dovetail shaped cutout on the other end.

Another embodiment relates to a fuel cell assembly including a stack ofsolid oxide cells, at least one baffle, a top block, and a base, whereinthe at least one baffle assembly is vertically aligned over the base andinterlocks with the top block.

Another embodiment relates to a spring compression assembly configuredto apply a load to a stack of electrochemical cells. The springcompression assembly includes a spring, a tensioner configured to applypressure to a first side of the spring and a bottom plate located on asecond side of the spring opposite the first side of the spring. Thebottom plate is configured to transfer load from the spring to the stackof electrochemical cells.

Another embodiment relates to a kit including a plurality of baffleplates configured to be attached to a side of a stack of electrochemicalcells and to place a load on the stack of electrochemical cells. Theplurality of baffle plates includes cutouts. The kit also includes aplurality of inserts configured to fit in the cutouts and interlock theplurality of baffle plates.

Another embodiment relates to a fuel cell system including a fuel cellstack located over a base and a plurality of side baffles locatedadjacent to at least two sides of the fuel cell stack, the plurality ofside baffles configured to provide a compressive stress on the fuel cellstack.

Another embodiment relates to a fuel cell system. The fuel cell systemincludes a fuel cell stack and an internal compression device that usesgravity and a mass of the fuel cell stack to provide a compressive forceon the fuel cell stack.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a three dimensional view of a prior art fuel cellassembly.

FIG. 2 illustrates a side view of an embodiment of a column of fuel cellstacks with plate shaped side baffles.

FIG. 3A illustrates a three dimensional view of an embodiment of plateshaped side baffles with dovetail connections.

FIG. 3B illustrates a three dimensional view of the embodiment of FIG.3A with a spring compression assembly attached to the side baffles.

FIG. 4 illustrates a three dimensional view of an embodiment of plateshaped side baffles with dovetail connections and bow tie/dog boneconnectors.

FIG. 5 illustrates a three dimensional view of an embodiment of plateshaped side baffles with dovetail connections and non-space filling bowtie/dog bone connectors.

FIG. 6 illustrates a three dimensional view of an embodiment of a springcompression device.

FIG. 7 illustrates a three dimensional view of another embodiment of aspring compression device.

FIG. 8 a three dimensional view of illustrates another embodiment of aspring compression device with a tension band.

FIG. 9 is a side view of a portion of the spring compression device ofFIG. 8 with an explanatory force diagram.

FIG. 10 illustrates a three dimensional view of an external bracketwhich may be used to supply compression to a spring compression device.

FIG. 11 is a micrograph illustrating the microstructure of a ceramicmatrix composite (CMC) that may be used in the side baffles, bow tieconnectors or leaf spring.

FIG. 12 is a micrograph of the CMC of FIG. 11 at a higher magnification.

FIG. 13 is a micrograph of the CMC of FIGS. 11 and 12 at a highermagnification.

FIG. 14 illustrates a side view of an embodiment of an internalcompression device.

FIG. 15 illustrates a side view of another embodiment of an internalcompression device.

FIG. 16 illustrates a side view of another embodiment of an internalcompression device.

FIG. 17 illustrates a side view of another embodiment of an internalcompression device.

DETAILED DESCRIPTION

The present inventors realized that the bores or feed-throughs 224decrease the system efficiency because they create heat sinks. Thepresent inventors also realized that the bores 224 can be eliminated anda compressive load applied to the fuel cell stacks 14 by redesigning thebaffles 220. By applying the compressive stress with the bafflesthemselves, the tie rods 222 can be eliminated, and thus, the bores 224can be eliminated. Thus, in one embodiment, the baffles lack bore holesthat extend vertically through the baffles and tie rods located in theholes.

FIG. 2 illustrates a first embodiment. In this embodiment, two sidebaffles 220 are placed on opposite sides of the column containing one ormore fuel cell stacks 14. However, more or less side baffles 220 may beused for stacks having a cross sectional shape other than rectangular.Further, one or more fuel manifolds 204 may be provided in the column offuel cell stacks 14. An exemplary fuel manifold is described in the U.S.application Ser. No. 11/656,563 noted above. Any number of fuelmanifolds 204 may be provided between adjacent fuel cell stacks 14 asdesired. Further, the number of fuel cell stacks 14 in a column of fuelcell stacks 14 may be selected as desired and is not limited to thenumber of fuel cell stacks 14 illustrated in FIG. 2.

In this embodiment, the side baffles 220 are used to place a compressiveload on the fuel cell stack(s) 14 (or column(s) of stacks). Thisembodiment eliminates costly feed-throughs and resulting tie rod heatsinks and uses the same part (i.e., side baffle 220) for two purposes:to place the load on the stacks 14 and to direct the cathode feed flowstream (e.g., for a ring shaped arrangement of stacks shown in FIG. 1,the cathode inlet stream, such as air or another oxidizer may beprovided from a manifold outside the ring shaped arrangement through thestacks and the exit as a cathode exhaust stream to a manifold locatedinside the ring shaped arrangement). The side baffles 220 may alsoelectrically isolate the fuel cell stacks 14 (or a column of stacks 14)from metal components in the system. The load on the stacks may beprovided from any one or more load sources, such as the base 239 of thesystem, a block underneath the stack 14 or column of stacks, a springassembly above the stack 14, etc.

Preferably, the ceramic side baffles 220 have a plate shape rather thanwedge shape and are made from plate shaped pieces or features (e.g.,baffle plates 202) rather than comprising a unitary ceramic piece. Plateshaped baffles and plates preferably have two major surfaces and one ormore (e.g., four) edge surfaces. In an embodiment, one or more edgesurfaces may have an area at least 5 times smaller than the majorsurface area. Alternatively, one or more edge surfaces may have an areaat least 4 times or 3 times smaller than the major surface area.Preferably, the plates have a constant width or thickness, have asubstantially rectangular shape when viewed from the side of the majorsurface, and have a cross sectional shape which is substantiallyrectangular. In an alternative embodiment, the ceramic side baffles 220are not rectangular but may have a wedge shaped cross section. That is,one of the edge surfaces may be wider than the opposing edge surface.However, unlike the prior art baffles 220 which completely fill thespace between adjacent electrode stacks 14, the side baffles 220 of thisembodiment are configured so that there is space between side baffles220. In other words, the side baffles 220 of this embodiment do notcompletely fill the space between adjacent fuel cell stacks 14.Preferably, the baffle plates 202 are made from a high temperaturematerial, such as alumina or other suitable ceramic. In an embodiment,the baffle plates 202 are made from a ceramic matrix composite (CMC).The CMC may include, for example, a matrix of aluminum oxide (e.g.,alumina), zirconium oxide or silicon carbide. Other matrix materials maybe selected as well. The fibers may be made from alumina, carbon,silicon carbide, or any other suitable material. Any combination of thematrix and fibers may be used. Additionally, the fibers may be coatedwith an interfacial layer designed to improve the fatigue properties ofthe CMC. If desired, the CMC baffles may be made from a unitary piece ofCMC material rather than from individual interlocking baffle plates. TheCMC material may increase the baffle strength and creep resistance. Ifthe baffles are made from alumina or an alumina fiber/alumina matrixCMC, then this material is a relatively good thermal conductor attypical SOFC operating temperatures (e.g., above 700° C.). If thermaldecoupling of neighboring stacks or columns is desired, then the bafflescan be made of a thermally insulating ceramic or CMC material.

The baffle plates 202 may be pieced together as shown in the FIGS. 3-5.For example, the ceramic plate shaped baffle plates 202 may be attachedto each other using dovetails 305, as shown in FIGS. 3A and 3B. Moregenerally, the ceramic plate shaped baffles 202 may include one or moreprotrusions 303 on one side and one or more cutouts 304 on the oppositeside. The protrusions 303 and cutouts 304 may be angled as in theillustrated dovetails 305 or may be rounded as in a typical jigsawpiece, or other suitable shapes. The protrusions 303 (and the matingcutout 304) may, for example, have a more complex shape such as ashamrock shape. As shown in FIG. 3B, the protrusions 303 (oralternatively the cutouts 304) may also be used to attach the baffles toa spring compression assembly 600 (discussed in more detail below) whichmay be used to add a compressive load to the fuel cell stack 14.

In an alternative configuration shown in FIG. 4, bow tie shaped ceramicinserts 406 are used to form a connection between baffle plates 202. Theinserts 406 preferably comprise plate shaped inserts having a narrowermiddle portion and two wider end or dovetail portions. The end portionsmay be rounded (i.e., a dog bone type bow tie shaped inserts). The endportions of the bow tie shaped inserts 406 are fitted into correspondingcircular or quasi-circular cutouts 304 in the baffle plates 202. In thisembodiment, the ceramic plate shaped baffle plates 202 may include oneor more cutouts 304 on opposite sides of the baffle plate 202. In thisconfiguration, the end portions of the inserts completely fill thecutouts. This configuration increases the overall strength of the baffle220 relative to the previous embodiment and provides less stress at thecontact point between the baffle plates 202. The inserts 406 maycomprise the same material (e.g., alumina or CMC) or a differentmaterial from the material of the baffle plates 202. Further,analogously to the previous embodiment, the bow tie shaped inserts 406may be used to connect the top baffle plate 202 to a spring compressionassembly 600 by placing the insert(s) in respective cutouts in the topbaffle plate 202 and an element (e.g., block 603) of the assembly 600.

In another alternative embodiment shown in FIG. 5, the inserts 406 donot completely fill the circular or quasi-circular cutouts 304 in thebaffle plates 202. The inserts 406 still have a generally bow tie shape,but include flat edges 501 rather than fully rounded edges. Thus, emptyspace 502 remains in the respective cutouts 304 above or below theinserts 406.

The baffle plates 202 may be attached to the base 239 of the systemusing a dovetail 305 with sharp edges, such as those in FIG. 3 or a bowtie shaped inserts 406, such as those shown in FIG. 4. In an alternativeconfiguration, FIG. 5 shows a column of stacks 14 attached to a linkageblock 503 located below the column rather than being attached directlyto the system base 239. The load on the column is provided from thelinkage block 503 to create a “cage” around the column. For example, thelinkage block 503 may comprise a ceramic material, such as alumina orCMC, which is separately attached (e.g., by the inserts, dovetails orother implements) to the ceramic baffles and to the system base 239. Theuse of the ceramic block material minimizes creation of heat sinks andeliminates the problem of linking the ceramic baffles to a metal basewhich introduces thermal expansion interface problems.

The dovetail protrusion 303 shown in FIGS. 3A and 3B preferably extendsfrom the base 239 or linkage block 503 into the bottom baffle plate 202.Alternatively, the bow tie shaped insert 406 may be used to attach thebottom baffle plate 202 to the base or linkage block 503 as shown inFIG. 5 by being inserted into respective cutouts in plate 202 and block503. However, in other configurations, the protrusion 303 may insteadextend from the bottom baffle plate 302 into the base 239 or the linkageblock 503. Any other suitable attachment methods other than dovetails305 or inserts 406 may also be used. FIGS. 4-5 also show fueldistribution manifolds 204 between the stacks in the stack column andfuel inlet and exhaust conduits connected to the manifolds.

FIG. 6 illustrates an embodiment of a spring compression assembly 600that may be used in conjunction with any of the side baffle assemblies220 described above. The spring compression assembly 600 may be used toapply a compressive load to a fuel cell stack 14 or column of fuel cellstacks 14. The spring compression assembly 600 includes a spring 611. Asillustrated, spring 611 is a ceramic (e.g., CMC or alumina) leaf spring.A CMC spring is advantageous because it may include creep resistantfibers arranged in a direction in the matrix which resists creep. Theceramic spring can exist in a high temperature zone and allow for travelfrom differential thermal expansion from components applying the load tothe stack. However, any other type of spring or combination of springsmay be used. For example, the spring 611 may be a coil spring, a torsionspring, or a volute spring.

The spring compression assembly 600 may include a bottom plate 607configured to provide a resilient surface against which the spring 611can generate a compressive load. Preferably, the bottom plate 607includes retention barriers 608 configured to prevent the spring 611from sliding off the bottom plate 607. When using a leaf spring, thebottom plate 607 may also include spring supports 604. In thisconfiguration, the spring 611 may be placed on top of the springsupports 604 (e.g., rod or bar shaped protrusions or ridges in plate607) in an unstressed condition (see also FIG. 7).

In an embodiment, an upper plate 601 is provided on top of the spring611, that is, on the opposite side of the spring 611 from the bottomplate 607. The upper plate 601 may include a spring tensioner 612, inthis embodiment a rod, on the bottom of the upper plate 601. The springtensioner 612 is preferably located approximately in the center of theupper plate 601. The spring compression assembly 600 may also beprovided with an upper block 603 which may include either cutouts 304(which accept inserts 406 from baffles as illustrated) or protrusions303 by which spring compression assembly 600 may be attached to the sidebaffles 220.

A temporary tightening mechanism may be attached over or to the springcompression assembly 600 during the process of connecting the assemblyto the baffles 220. In the embodiment of FIG. 6, this mechanism includesa bracket 602. The bracket 602 may be affixed to the bottom plate 607 bybolts as illustrated or by any other suitable mechanism. Movablyattached to the bracket 602 is a temporary tensioner which in thisembodiment comprises a pressure plate 605. As illustrated, the pressureplate 605 is movably attached to the bracket 602 by way of rods 609which slide in elongated slots 606.

The compression load applied by the spring compression assembly 600 maybe adjusted via a pressure adjusting mechanism 610. The pressureadjusting mechanism 610 may be, for example, a screw or bolt which maybe raised or lowered by rotating. In the embodiment illustrated in FIG.6, lowering the pressure adjusting mechanism 606 causes the pressureplate 605 to travel downward. As the pressure plate 605 lowers, itforces the upper block 603 and the upper plate 601 to lower as well.When the upper plate 601 lowers, the spring tensioner 612 is forcedagainst the center of the spring 611, causing it to bend and therebyapply a load to the spring 611.

In use, the pressure adjusting mechanism 610 is lowered (and the spring611 compressed) until the upper block 603 can be connected (e.g.,hooked) to the side baffles 220. Once the side baffles 220 are connectedvia dovetails, inserts or other implements, the pressure adjustingmechanism 610 is loosened to release the bracket 602. The force of thespring 611, previously “held” by the pressure adjusting mechanism 610,is now transferred to the side baffles 220. Adjustment of thecompressive force on the stack may be attained by fitting shims (notshown) between the spring compression assembly 600 and the top of thestack 14 (which sits below the bottom plate 607 of the springcompression assembly 600). More shims create a tighter compression. Thepressure adjusting mechanism 610 provides pretension to allow connectionof the assembly 600 to the side baffles 220. The bracket 602, includingmechanism 610 and elements 605, 606 and 609 are then removed from thefuel cell column before the column is placed into an operating mode.

FIG. 7 illustrates another embodiment of a spring compression assembly600A. This embodiment is similar to the previous embodiment. However,the rod shaped spring tensioner 612 is replaced with a dome shapedspring tensioner 612A, where the curved side of the dome is in contactwith the upper surface of the spring. Rod shaped spring supports 604contact edge portions of a lower surface of the spring 611 to inducebending in the spring. Additionally, this embodiment includes spacers702 which reduces the distance between the block 603 and the spring 611,thereby reducing the amount of adjustment required with the temporarytightening mechanism, such as a bolt or screw (not shown for clarity) toapply a load to the spring 611 through opening 610A.

FIGS. 8 and 9 illustrate yet another embodiment of a compressionassembly 600B. In this embodiment, the assembly includes tension band802 located below the block 603. The assembly 600B preferably uses thetension band 802 in place of the leaf spring. However, if desired, thetension band may be used in combination with a spring described in priorembodiments. The tension band 802 may be attached to pull rods orhandles 609 via buckles or other attachments 804. In this embodiment,the rods 609 are pulled apart by an external mechanism (not shown) tostretch the tension band 802 and exert a downward force on the springtensioner 612B. In this embodiment, the tensioner 612B may be an upwardsfacing dome which receives the downward force from the band 802. Theband 802 is permanently retained in the assembly 600B and the band ismade of a high temperature tolerant material. As illustrated in FIG. 9,the force in the tension band 802 is related to the yield strength ofthe tension band 802 material, the amount of deflection θ of the tensionband 802 and the length L of the tension band 802 (which is varied bythe amount of force exerted on the handles 609). Thus, the amount ofcompression added to the stack can be precisely predetermined byselecting the material, length L and amount of deflection θ.

FIG. 10 illustrates another embodiment of a temporary tighteningmechanism which comprises an external bracket 1002 which may be used tosupply compression to a spring compression assembly 600C (e.g., anassembly comprising a dome tensioner similar to that shown in FIG. 7).In this embodiment, two external brackets 1002 may be assembled on topof the spring compression assembly 600C via flanges 1004 in the brackets1002. Pressure may be applied to the external brackets 1002 by applyingforce to the top of the external brackets 1002 or pulling down on theexternal brackets by attachment of an external force to the externalbrackets 1002 via holes 1008 in the external brackets 1002. Whensufficient compression of the column of fuel cell stacks 14 is achieved,a bow tie insert 406 may be inserted through an opening or window 1006in the side of the external bracket 1002 to attach the side baffle 220to the upper block 603.

Thus, as described in the above embodiments, the thermal expansion ofthe stack or column (the element compressed) should be balanced againstthe thermal expansion of the clamping mechanism (which is primarily thebaffles and/or the spring) such that the desired amount of force on thestack or column is attained when the stack or column reaches operatingtemperature.

Furthermore, as described in the above embodiments, the compressionmechanism (i.e., the compression assembly 600 to 600C) is connected tothe baffles 220 by attaching a temporary tightening mechanism, such asthe above described bracket, bolt or screw over the compressionmechanism 600 to 600C, providing an additional compressive stress on thestack 14 and the compression mechanism using the tightening mechanism(e.g., lowering the pressure plate in a bracket, tightening the bolt orscrew, stretching the tension band, pulling down on the bracket, etc.),coupling the compression mechanism to the side baffles (e.g., usingdovetails 305 or inserts 406 to attach the block 603 to the top baffleplate 202), and removing the temporary tightening mechanism.

FIGS. 11-13 are micrographs of a representative CMC that may be used forthe spring element 611. The side baffle plates 202 and/or the inserts302 may also be made of a CMC material. The CMC illustrated in FIGS. 7-9have an alumina matrix and alumina fibers. Other CMC materials may beused. The particular CMC illustrated has a matrix with elongated grainsand fibers having circular or ellipsoidal cross sections. Othermicrostructures may also be used including, but not limited to, equiaxedgrains and woven fibers. In the illustrated embodiment, the fibers havea diameter of approximately 12 microns. Fiber with other diameters maybe used including, but not limited to 1, 2, 3, 4, 5, 10, 15, 20, 25, 50,and 100 microns.

FIGS. 14-17 illustrate embodiments of fuel cell stacks 14 with aninternal compression device 1400. The internal compression devices 1400are configured to use gravity and the mass of the fuel cell stack 14 toprovide a compressive force on the fuel cell stack. FIG. 14 illustratesan embodiment in which the internal compression device 1400 includes arigid cross member 1402 located across the top of the fuel cell stack14. Attached to the rigid cross member 1402 by means of a pivot member1403 and located adjacent to at least two sides of the fuel cell stack14 are tension members 1404. The internal compression device 1400 alsoincludes levers 1406 attached to the tension members 1404 (e.g., wiresor rod). The levers 1406 are located below the fuel cell stack 14.Further, the levers 1406 are configured to transfer force due to themass of the fuel stack and gravity to the tension members 1404 andthereby provide compressive force on the fuel cell stack 14.

FIG. 15 illustrates another embodiment of the internal compressiondevice 1400. This embodiment also includes a rigid cross member 1402located across the top of the fuel cell stack 14, tension members 1404located adjacent the sides of the fuel cell stack 14 and levers 1406located below the fuel cell stack 14. In this embodiment, however, thefuel cell stack may include a plate 1408 made of a high coefficient ofthermal expansion (CTE) material under the rigid cross member. As thetemperature increases in the fuel cell stack 14, the plate 1408 expandsgenerating upward stress on the rigid cross member 1402 and downwardstress on the fuel cell stack 14.

In other aspects of this embodiment, the high CTE material may havealternative (that is non-plate) shapes. In this embodiment, the levers1406 and the tension members 1404 are configured so that there is littleor no force applied to the fuel cell stack 14 at room temperature. Thehigh CTE material and its shape are selected so that when the fuel cellstack is at its operating temperature, the force generated by theexpansion of the high CTE material generates a preselected compressiveforce which is applied to the fuel cell stack 14 via the tension members1404 and the levers 1406.

FIG. 16 illustrates another embodiment of the internal compressiondevice 1400. In this embodiment, the top of the fuel cell stack 14 hasrounded edges 1010. Additionally, the internal compression device 1400includes a strap 1412 over the top of the fuel cell stack 14 and runningdown at least two sides of the fuel cell stack 14. The strap may bemade, for example, of a woven ceramic material 1413. Attached to theends of the strap and located below the fuel cell stack 14 are levers1406. The levers 1406 are configured to transfer force due to the massof the fuel stack 14 and gravity to the strap 1412 and thereby providethe compressive force on the fuel cell stack 14.

FIG. 17 illustrates still another embodiment of the internal compressiondevice 1400. In this embodiment, the top and the bottom of the fuel cellstack 14 have rounded edges. The internal compression device 1400,however, includes a closed loop belt 1414 around the periphery of thefuel cell stack 14. As in the previous embodiments, the internalcompression device includes levers 1406 below the fuel cell stack 14.The levers 1406 are attached to the closed loop belt. The mass of thefuel stack 14 and gravity act on the levers 1406 and thereby provide thecompressive force on the fuel cell stack.

Although the foregoing refers to particular preferred embodiments, itwill be understood that the invention is not so limited. It will occurto those of ordinary skill in the art that various modifications may bemade to the disclosed embodiments and that such modifications areintended to be within the scope of the invention. All of thepublications, patent applications and patents cited herein areincorporated herein by reference in their entirety.

What is claimed is:
 1. A spring compression assembly configured to applya load to a stack of electrochemical cells comprising: a ceramic leafspring; a tensioner configured to apply pressure to a first side of theceramic leaf spring; and a bottom plate located on a second side of theceramic leaf spring opposite the first side of the ceramic leaf spring,the bottom plate configured to transfer a load from the ceramic leafspring to the stack of electrochemical cells; and a ceramic blocklocated on an end of the stack of electrochemical cells, the ceramicblock interlocking with baffles located on one or more sides of thestack of electrochemical cells, wherein the tensioner comprises a domeshaped tensioner having a curved side in contact with an upper surfaceof the ceramic leaf spring, and further comprising cylindrical rodshaped spring supports contacting edge portions of a lower surface ofthe ceramic leaf spring.
 2. The spring compression assembly of claim 1,wherein the tensioner comprises a rod which exerts a downward force on acentral portion of an upper surface of the ceramic leaf spring.
 3. Thespring compression assembly of claim 1, wherein the ceramic leaf springcomprises a ceramic matrix composite (CMC) material and wherein theelectrochemical cells comprise solid oxide fuel cells.
 4. A solid oxidefuel cell assembly, comprising: the spring compression assembly of claim1, the stack of electrochemical cells comprising a stack of solid oxidecells; and a baffle assembly configured to place a load on the stack ofelectrochemical cells and direct a reactant feed flow stream to thestack of electrochemical cells.
 5. The assembly of claim 4, wherein thebaffle assembly comprises a first vertically aligned baffle plate on afirst side of the stack of electrochemical cells and a second verticallyaligned baffle plate on an opposite second side of stack ofelectrochemical cells.
 6. The assembly of claim 5, wherein the baseinterlocks with bottom of the first and second vertically aligned baffleplates.
 7. The assembly of claim 6, wherein the first and secondvertically aligned baffle plates do not comprise a through hole andwherein the reactant is an oxidant.
 8. The assembly of claim 4, whereinthe first and second vertically aligned baffle plates comprise a ceramicmaterial.
 9. The assembly of claim 8, wherein the ceramic materialcomprises a ceramic matrix composite (CMC).
 10. The assembly of claim 9,wherein the CMC comprises a matrix comprising aluminum oxide, zirconiumoxide or silicon carbide, and fibers comprising aluminum oxide, carbonor silicon carbide.
 11. The assembly of claim 4, wherein: the stack ofelectrochemical cells is located in a column of solid oxide fuel cellstacks; the bottom plate is located over only a single column of solidoxide fuel cell stacks; and the spring compression assembly containingthe ceramic leaf spring is located above the single column of solidoxide fuel cell stacks and is configured to apply the load to the singlecolumn of solid oxide fuel cell stacks.
 12. The spring compressionassembly of claim 1, wherein the rod shaped spring supports contact onlyedge portions of a lower surface of the ceramic leaf spring.
 13. Thespring compression assembly of claim 1, wherein the ceramic blockcontains cutouts configured to accept inserts from baffles to interlockthe ceramic block with the baffles.